The intent of this application is to request funds for the training minority students in the field of developmental neurobiology. The main objective of the proposal, in which the students will be involved, is to examine factors that regulates the development and expression of neurotransmitter phenotypes in the central nervous system (CNS) of the chick. In our current MBRS grant period we sought to establish the chick embryo as an experimental model for such development studies, and completed an extensive analysis of the ontogenesis of central serotonergic (5-HT) neurons in the brain and spinal cord. The information provided by these pervious studies serves as a basis for the present proposal which includes the following specific aims: (1) An immunocytochemical description of the initial development of several additional transmitter phenotypes in the chick CNS. The phenotypes selected for study are of interest because of their possible co-existence with 5-HT neuronal systems. (2) A further examination of the regulation of the expression of the 5-HT phenotype in a unique population of 5- HT neurons intrinsic to the spinal cord. Of interest are the changes in the number of cells expressing this phenotype during embryonic and post-hatching development. (3) An initial attempt to manipulate the expression of these spinal cord 5-HT neurons during development utilizing in vitro cultures of dissociated spinal cord cells and in ovo microsurgical techniques. The overall intent of these studies is to define the timing and potential mechanisms responsible for neurotransmitter phenotype determination, expression and possible plasticity in the chick CNS. The exposure of undergraduate minority students to the exciting field of development neurobiology and to the various current techniques proposed for use in this application will hopefully encourage their consideration of continuing their education and training for careers in biomedical research.